JPH02185904A - Hot pressing of powder and granule - Google Patents

Abstract

PURPOSE: To produce a molded part having high dimensional precision and high density in a short time by subjecting metallic particulates at temp. between the recrystallization temp. and the solidus temp. to hot pressing in a heated and lubricated die cavity, thereafter moving the same to an another part and executing pressurizing. CONSTITUTION: Metallic particulates or metallic alloy particulates 12 are heated to a temp. in the range from approximately the recrystallization temp. thereof to the solidus temp., preferably in an inert gas atmosphere within a box 22 and is carried into a hot pressing device having a heating die 14. The particulates subjected to the heating are subjected to hot pressing under primary pressure by an upper end punch 24 and a bottom punch 26 in a heated and lubricated primary part within a die cavity 18 of the main body 16 the die. In this way, the particulates 12 are pressed substantially to a molding 11 and is solidified. Then, the molding is moved to a secondary part in the die cavity 18, where it is pressed under secondary pressure higher than the primary pressure and is densified approximately to theoretical density. The obtd. molding 11 is discharged by lifting the bottom punch 26, is, if required, carried into a cooling tank 32 by a moving device 28 and is rapidly cooled.

Description

TECHNICAL FIELD This invention relates to the production of precision metal moldings from metal or metallic particles, and to a method and apparatus for compressing and consolidating such particles at high pressures and temperatures.

[Background technology]

From a commercially significant point of view, the use of powdered metals to make molded articles has been largely limited to aluminum powder or other powdered metal materials and products thereof. The present invention goes beyond powder metallurgy technology and extends the limits of use of powder and granular materials to include iron, lead, magnesium, copper, molybdenum, and other materials as well as aluminum, in addition to the metals commonly used therein. The purpose is to Further, according to the present invention, the hot-pressed granular material is formed into a molded article having excellent properties that allow the molded article to be used in applications not previously thought possible. As detailed later,
It is possible to produce precision molded articles directly by hot pressing techniques that have sufficient strength, dimensional accuracy and surface properties so that the molded articles can be used directly or with minimal mechanical manipulation.

The most common and therefore the most appropriate reference for the state of the art for producing shaped articles from granular metal is aluminum powder metallurgy technology. Typically, aluminum powder metallurgy methods require the use of pure aluminum metal powder, which is lubricated and cold compacted in a die to form a green product. The green product is then sintered for 20 minutes in a protected environment. The sintered product is deformed to some extent and then recompressed or coined by a compressor,
A final molded article is obtained. Aluminum powder metallurgy molded parts produced by this method are generally brittle and have some degree of porosity, and the high tensile strength of molded parts machined from annealed and forged aluminum rods. It lacks.

On the other hand, the hot pressing method of the present invention can be used with pure aluminum metal or aluminum alloy materials, and can also use aluminum metal scrap, commonly called "swarf J". According to the hot compaction method of the present invention, aluminum or aluminum alloy materials can be processed using the hot compaction method of the present invention, as opposed to the cold compaction, sintering and coining operations used in powdered aluminum metallurgy as described above. can be directly and quickly hot pressed into the desired shape with precisely dimensioned surfaces.

Additionally, the particles are strain hardened during hot compaction into precision dimensioned products, resulting in improved mechanical properties more similar to cast-formed annealed products at the cost of an annealing process. It has been found that it can be provided without

There has also been some research into hot pressing aluminum particles into sheets, as disclosed, for example, in US Pat. No. 3,076,706. The hot compaction process disclosed therein differs substantially in that a different pressure-temperature relationship is used and the sheet is formed between rolls having open passages at both ends thereof. More specifically, the sheet is formed between water-cooled rolls at a temperature at the nip of the rolls that is approximately half the temperature to which the aluminum particles were preheated. Furthermore, the calculated pressure is approximately 844 Kylcr! (12,000p,
s, i), and the resulting sheets generally had fibrous-like properties. Typically, after forming, the sheet is thinned by cold rolling and then annealed to about 315
．． Crystallization at 6°C (600↑) provides desirable physical properties as a sheet. However, in the present invention the pressure is substantially higher, e.g.
44-7030 K9/, 1 (12,000-100,
0 OOP, S, I), the temperature used is more (, a non -fibrous product is obtained.

Grain growth is avoided and metal products are manufactured using U.S. Patent No. 3076.
．． It has properties more similar to plastic kneaded aluminum products than the tighter cold worked fibrous metal products made in No. 706. Furthermore, products made by the hot pressing technique of the present invention can have an annealed appearance even though they are not annealed.

The present invention also allows the product to be manufactured with relatively thick cross-sections, e.g. 1.27 cm, at high temperatures and pressures without welding or sticking to the die.
The present invention has a preferred apparatus capable of forming products having a diameter of m ('/2 inch) or more. According to the present invention, aluminum particles can be hot-pressed in a die made of conventional tool steel that can withstand the relatively low temperatures of 400-600°C used in hot-pressing processes. The problem of material sticking to the die can be further alleviated by using a die lubricant such as graphite or other materials. For thicker cross-sectional products, hot compaction provides an initial compaction of the particles to substantially eliminate primary voids in the first section of the die. Two-step or staged compaction in a single die can be used. Preferably, the apparatus will have an automatic die lubrication system. Furthermore, large particles do not aggregate and mix freely.
It has been found that it is preferable to keep it moving by stirring or otherwise to fill the cavity of the hot compression die. If desired, the heated aluminum particles can be kept in a protective atmosphere in the feed box to the die;
The actual compression can take place in the ambient environment. The reason is that relatively short compaction times are used in the compaction operation.

[Disclosure of the invention]

SUMMARY OF THE INVENTION Accordingly, it is a general object of the present invention to provide a new and improved hot compacted granular molded article and to provide a method and apparatus for making molded articles such as cages.

A more specific object of the invention is to provide a new and improved plastically worked metal product made from compacted aluminum or aluminum alloy powder particles that have been hot pressed at high temperatures and pressures to provide a strain hardened product. It is in.

Still another object of the present invention is to provide a method and apparatus capable of molding a precision product with good mechanical properties within 30 seconds from a low-friction powder raw material.

These and other objects of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram of an apparatus for carrying out the method of hot compaction of metal or metallic particles according to the present invention.

FIG. 2 is a graph showing the effect of temperature change on the difference in thickness of molded articles manufactured according to the present invention.

FIG. 3 is a graph showing the effect of temperature changes on the surface finish of hot pressed molded articles made in accordance with the present invention.

FIG. 4 is a graph showing the effect of pressure on the surface finish of molded articles made in accordance with the present invention.

FIG. 5 is a graph showing the effect of pressure on the difference in Rockwell hardness between different locations in a molded article made in accordance with the present invention.

FIG. 6 is a graph showing the effect of temperature change on the Rockwell hardness of molded articles manufactured according to the present invention.

FIG. 7 is a graph showing the effect of temperature change on the ultimate tensile strength of molded articles made according to the present invention.

FIG. 8 is a graph showing the effect of pressure changes on the flash thickness of molded articles manufactured according to the present invention.

FIG. 9 is a graph illustrating the effect on Rockwell hardness of molded articles hot compacted at temperatures below and substantially above the homeophase temperature.

FIG. 10 is a graph showing the effect of hot compaction on ultimate tensile strength at temperatures below and above the solidus temperature.

Figures 11, 12, 13 and 14 are enlarged photomicrographs of etched cross-sections of hot-pressed molded articles formed by hot-pressing granular materials according to the present invention.

FIG. 15 is an enlarged microscopic photograph of an etched cross section of a hot-compressed molded product formed by hot-compressing the magnesium powder described in Example 5 below.

FIG. 16 is an enlarged microscopic photograph of a chiseled cross section of a hot-compressed molded product formed by hot-compressing the magnesium powder described in Example 6 below.

FIG. 17 is an enlarged microscopic photograph of an etched cross section of a hot-pressed molded product formed by hot-compressing the copper powder described in Example 7 below.

As shown in the drawings for illustrative purposes, molded articles 11 may be formed by hot pressing heated particles 12 in a hot pressing apparatus having a heated die 14 . The illustrated die consists of a heated die body 16 having an internal cavity 18 filled with preheated granules from a heated supply means or box 22 in which the preheated granules are stored. The die can take on a variety of shapes and configurations, but here it is connected to a conventional compressor that moves downward into the die cavity to compress the charge of powder at the desired pressure and in a given amount of time. The upper bunch 24 is shown as having a curved top bunch 24. bottom bunch 2
6 is movable upward into the die cavity in order to project the compacted molded product from the die cavity. The ejected part can be moved laterally from the die by a transfer device 28 which can move the part to a quench bath 32 if quenching is desired.

According to the present invention, the molded article 11 formed from hot-pressed metal or metallic powder has properties superior to those obtained from directly cast metal, using a unique hot-compression method.
It has strength and other properties and can be manufactured to have a tensile strength greater than that of a cast part and close to that of a plastically worked part formed by processing a cast part. Furthermore, the molded articles of the present invention appear to have a more isotropic tensile strength than cast molded articles of the same metal. Although these molded articles were not subjected to normal annealing or heat treatment after molding,
It appears to have been cold worked and annealed to give a plastically worked molded part. The granules used in the preferred hot compaction method are relatively large compared to the powder particles, and these larger granules, when consolidated in a die at high temperatures and pressures, allow a sufficient amount of metal to be processed. It is thought that the

However, it does not seem to be certain that the particles become strain hardened as they are deformed and compressed, thus creating voids between them. Preferred molded articles with high densities substantially close to the theoretical density are produced. Additionally, the external surfaces of these molded parts are smoother and held to closer tolerances than the external surfaces of cast molded parts.

According to the present invention, existing die compactors are used to hot-compact molded parts 11 at relatively high speeds, and the molded parts 11, such as aluminum or aluminum alloys, do not weld themselves to the die or have relatively thick sections. When using materials that are generally considered impossible to mold into products with an area of 11.
can be manufactured economically and repeatedly from die 14.

More specifically, in accordance with the present invention, a preferred method (preferably with a surface area to volume ratio of 3 to 1,000) is to fill the die cavity 18 with a flowable metal or metal alloy powder 12. the particles are preheated (as in preheat box 22) to a temperature ranging from about the recrystallization temperature of the metal or alloy to about the solidus temperature of the alloy (i.e., the melting point of the metal) and die cavity 18. is heated to a temperature sufficient to maintain the powder in the temperature range during subsequent hot compaction, and the preheated powder is heated to a sufficient pressure [e.g.
30 kg/c! t(12,000~100,000p
, s, i, )) for a period of less than 30 seconds, while maintaining the particles in the temperature range, to solidify the powder into a dense molded article, and the product is It consists of removing from the heated die cavity 18. This preferred method and the molded articles formed therefrom are carried out using granules in the form of particles of larger particle size than normal powder particles. This is because such larger size particles do not tend to sinter weld together when preheated, and larger size particles are less susceptible to cold opening and/or processing which is not possible with fine powder particles. This is thought to be due to strain hardening.

As used herein, [particulate
e) The term J refers to preferred larger size particles having a surface area to volume (SA/V) ratio in the range of about 3 to 1000 and an SA/V ratio of 1500 or greater, such as typically sulfur aluminum powders. Includes powder.

Accordingly, as used herein, the term "powder" refers in an inclusive sense to larger particles and smaller powders, and the term "particle J" refers to particles with an SA/ Used to mean a metal piece with a V ratio.Hereinafter, it is used to mean a metal piece with a SA of substantially more than 1000.
/V ratio metal pieces are called "powders"
I'll call it J.

As used herein, surface area to volume ratio is defined as surface area in square inches divided by volume in cubic inches. Therefore, this relationship is expressed in inches to powers of 10-1.

Of course, a similar division can also be performed for the area expressed in square millimeters divided by the volume expressed in cubic millimeters. In a preferred method 4, the molded article is compressed with sufficient pressure to have a density of about 99% of the theoretical density. Additionally, the particles can be heated and hot compacted at about the solution annealing temperature of the metal or alloy and then age hardened to further strengthen the product.

The particles are hot compacted for a short time (less than 30 seconds) above their recrystallization temperature (and below their solidus temperature), and then the grains in the particles are recrystallized and grown or annealed. It is an important aspect of the method of the invention that the product is cooled below the recrystallization temperature (below the recrystallization temperature) before it is cooled for less than 4 seconds at a temperature above the recrystallization temperature and below the solidus temperature. It is hot compacted and then removed and quickly cooled below the recrystallization temperature, thus preventing substantial grain growth and any substantial annealing. It has been found that the compacted bacteria are hard rather than soft, if the hot compaction temperature [about the solidus temperature]
dus temperature) J, i.e., higher than the melting point (so high that a significant part of the particles becomes liquid before or during compaction,
Hardness and tensile strength are significantly impaired. As used herein, "about the solidus temperature"
The term J is intended to include temperatures as much as 10 or even 20 inches above the theoretical solidus temperature. The reason is that at these temperatures, which are slightly above the theoretical, i.e., correct "solidus temperature" for the alloy, there is not enough liquid coming from the particles to substantially adversely affect the results. .

In addition, articles made from particles of generally uniform shape and size and hot-pressed according to the present invention will have a higher lateral and longitudinal extent than a cast or plastically worked article of the same metal or alloy. It can provide more uniform isotropy such as tensile strength. By preheating and then hot pressing homogeneous particles, e.g. needles or spheres of substantially uniform size, the particles do not lose their shape and aggregate, resulting in better isotropy for molded parts. forming a uniform-looking matrix or lamina-like cross section.

In contrast to the usual porosity found in powder metallurgy moldings, molding 11 has virtually zero porosity and complete density;
That is, it can be manufactured to have a density equal to about 100 inches of the theoretical density. These dense molded articles have also been found to be significantly more leak-tight to oil or gas than the more porous sintered powder aluminum metallurgy products or die cast aluminum products. The microstructure of this part is similar to that of a fully annealed part, even though no annealing was performed. The surface properties of the molded parts are very good, very uniform and very reproducible with respect to hardness and dimensional tolerances.

Looking at the preferred method in more detail, one form of particle that has been used successfully to date involves pouring molten aluminum into a perforated rotating cup and using centrifugal force to force the powder needles to emerge from the perforations. Acicular aluminum particles formed by cutting. A general description of one method for forming aluminum particles is disclosed in US Pat. No. 3,241,948.

Preferred particles are fairly uniform in size and have minimal oxidation. The aluminum needle-like body has a diameter of 2.54 to 6635 mm (0
, 1 to 0.25 inches) in length and approximately 0.38 inches in length,
015 inches) have been used. The apparent density of aluminum needles ranges from approximately 1.39/cx for coarse needles to 1 for finer needles.
．． 1;l/CC, the latter being close to the apparent density of conventional aluminum powder of 1.1 g/CC.

The raw material used to form the aluminum needles may be scrap aluminum, which usually contains some type of alloy metal therein. Scrap (usually "shavings"
arf ) J) is cleaned and degreased, then
It is melted in a furnace, poured into a perforated rotating cup, and rotomolded into a needle.

By rotating at a constant speed and temperature, the resulting aluminum particles are uniform in size, highly glossy, and have a uniformity of 100 aIJ of molten aluminum poured into the cup.
It has a utilization rate close to . Approximately 6.35 mm ('/4 inch)
Aluminum particles of length have been used advantageously.

Other significantly larger aluminum particles, e.g. -side 4.7
A 6 m x 3/6 inch cube was also hot pressed according to the method of the present invention. Spherical particles are even more advantageous because they have a smaller surface area to volume ratio (and better packing properties in the die). preferred for obtaining sex.

Instead of melting scrap and reshaping it into acicular or spherical particles, scrap machine shop drill bits and chips can be shredded to the desired size in a hammer mill and then hot compacted in a die. That is, if the shavings are small enough, they can be used directly in the hot pressing process.

The particles are preheated to a hot compaction temperature of about tl and then inserted into the die cavity 18. Preferably, the particles are preheated within a device such as feed box 22 by a resistive heater (not shown), and the inert hot gas prevents substantial oxidation of the particles while they reside within the feed box. It is saved and passed. Similarly, the particles are agitated while in the feed box by being vibrated by vibrating means (not shown) to prevent particles from sticking together while in the feed box. Preferably, the particles are at or slightly above ripeness at which subsequent hot compaction occurs to account for the temperature loss during transfer from the feed box to the heated die 14.

The extremely short time it takes to compact the particles, remove the molded product from the die, and cool it below the recrystallization temperature is not only a key factor in the properties obtained for the molded product itself, but also makes it cheaper than ever before. It is also a major factor in the economics of manufacturing molded articles. In contrast, the typical time for compression sintering of powder in powder metallurgy is 20 minutes, and subsequent heat treatment operations require hours or tens of minutes.

A supersaturated solution is obtained by quenching in water or other liquids, and the shaped articles are then naturally aged at room temperature. For example, a hot-pressed aluminum molded product is naturally aged for 4 days at room temperature to obtain a T-4 heat treated aluminum molded product. If desired, the aluminum part can be further heat treated to a T-6 condition by subjecting it to a temperature of about 121°C (250"F) for about 18 hours. For most metals, precipitation hardening The many different alloying agents that may be used are well known.Although only aluminum has been specifically mentioned as being precipitation hardened, it will be understood that other metals such as magnesium or steel may also be precipitation hardened.

[Best mode for carrying out the invention]

Although one particular example, an aluminum alloy, will be discussed in more detail below with respect to the various parameters of temperature, pressure and time, other parameters for other metals may also be obtained and verified. For pure metallic aluminum particles, the temperature is such that some melting of the aluminum occurs66
The solidus temperature of 0°C is not exceeded. Similarly, the temperature, recrystallization temperature and solidus temperature of aluminum will vary with the amount of alloying material. Generally, the temperatures used in this process will be on the order of the recrystallization temperature of about 400°C for aluminum alloys to the solidus temperature of about 600°C. The solution annealing temperature will be closer to the solidus temperature than the recrystallization temperature for aluminum alloys.

Better mechanical properties are obtained by hot compacting the aluminum alloy particles at higher temperatures, close to the solidus temperature. This is because about 42
For example, as described for aluminum alloys that are hot pressed at temperatures of 7-482°C (800-900"F),
), the particles will be more plastic and will consolidate and fill crevices and details within the mold. That is, the particles appear to be more plastic and flow and weld more easily at higher temperatures than at lower temperatures near the recrystallization temperature.

However, a temperature of approximately 482°C (900'F) is still below the solidus temperature (if the particles are hot compacted above the melting temperature and a significant amount of the particles will melt). It will be appreciated that a significant reduction in properties occurs.

The aluminum particles can be hot-pressed in just a few seconds at temperatures of 482°C (900°F), allowing the use of dies made from common industrial steel. This is in contrast to the more expensive superalloy metals, which must be used in processes that require higher temperatures and longer compression times. Because of the relatively short residence time, the metal particles are not highly oxidized.It should be understood that the particles may be heated in a variety of ways other than those described herein.

Preferably, the heated metal alloy particles are heated in the box for a sufficient time to a temperature that allows the alloy components to become a solid solution for subsequent precipitation hardening.

The preferred hot compaction operation is accomplished in an ambient environment, but if less oxidizing power is desired, particularly for ferrous particles heated to higher temperatures, e.g. A protective atmosphere is used around the heated particles while being transported and hot-pressed therein.Normally, a vacuum does not need to be used at the die as it introduces additional manufacturing costs. However, some conventional hot-pressing techniques use a vacuum to compress ferrous particles into 9
When hot compacting at temperatures above 82°C (1800°F), the heated die 14 is fabricated from a more expensive superalloy metal to provide the necessary strength and longevity for the die at these higher compaction temperatures. There is a need to.

The temperature range for hot compacting other particles varies, but
Preferably, the copper or copper alloy particles are hot compacted at about 600-800<0>C. Magnesium particles can be hot compacted at about the same temperature as used for aluminum or aluminum alloy particles.

Generally, it is preferred that the method be isothermal with respect to the die 14 and the particles being preheated to the hot compaction temperature. This preheating is usually done because the hot compaction time is so short that the molded article cannot be uniformly heated throughout during this very short compaction time. Here, the upper and lower compression rams are not heated, only the mold walls defining the cavity are preheated.

Hot compaction pressures vary depending on the particles used and the desired density of the product. In the case of aluminum alloy particles, 847~
7030 shame/(-d(12,000~100.000p
, s, i, ) is sufficient to compress the aluminum particles into a molded article having substantially 100% full theoretical density. For lower densities, the pressure may be lower. Once full density is achieved in the molded article by applying a certain pressure, applying additional higher pressure only tends to bond or weld the molded article to the sidewalls of the die. Also, applying higher and excessive pressures causes the hot compacted metal to penetrate further into the interstitial space of the die, resulting in a greater thickness of the die that would normally be removed later. FIG. 8 shows the increase in the thickness of the burr as the hot compression pressure increases.

Approximately 847-3515K at 510°C (950°F)
y/crl, (12,000~50,000 p, s
, i-), the pressures used on the aluminum do not easily damage the tool steel die, and the die can be used repeatedly to produce particles on a production scale.

Aluminum and aluminum alloys are used in hot pressing or powder metallurgy processing. At high temperature and high pressure, it has an affinity to weld or alloy to the die wall by itself. The walls of the die cavity 18 are lubricated with conventional graphite or lubricant to reduce the possibility of molded parts sticking to the die walls. Particle movement in the die during hot compaction is considerable. This is because the height of the hot compacted part is approximately the height of the particles filling the die before compaction.

Significant particle movement along the die wall during hot compaction can wipe lubricant from the die wall, after which the die wall is generally left unprotected during the final portion of the compaction cycle.

According to the present invention, the problem of welding or adhesion of hot-compacted particles to the die wall is solved because the initial and primary compaction takes place in the first part of the die, and the final solidification to a higher density is This problem was overcome by a multi-stage hot pressing process performed in a second, separate section of the die. The initial compaction of the particles reduces the fill volume in the goo to about the final size of the molded article and subjects the particles to a coarser movement, thereby scraping some of the die column lubricant from the die wall. Welding of a part to a non-lubricated area of the die wall involves the migration of a partially solidified part in the die to areas that are not filled with particles and, therefore, from which the die lubricant has not been scraped. This can be avoided by letting

A final and usually higher pressure is then applied in this second part of the die. The final pressure usually solidifies the molded article to a final density equal to or close to its theoretical density, and this final pressure is usually significantly higher. For example, scrap metal aluminum particles are
1.2Kf/c++! It is compacted to a theoretical density of about 85 yen by a very low pressure of (4000 p, s-1,) and then moved upward into the die cavity where the lubricant still remains. At this point, the upper die further compacts the particles to more than 99% of their theoretical density, and the particles fill most of the internal voids, approximately 1687 K9/cd (24,0
00p, s, i,) undergoes relatively small movements along the die wall during this final 15-chi compaction.

The whole process still takes less than 10 seconds,
The first step takes only 1-2 seconds, and the final pressure application also takes only 1-2 seconds.

The difference between the single-stage and two-stage hot compaction methods is obvious in that molded products manufactured using the single-stage method are more likely to have longitudinal streaks on their outer surfaces when compared to molded products manufactured using the two-stage method.

Typical lubricants are graphite or boron nitride. Residues of lubricant on the external surface of molded parts produced in a two-stage process are even advantageous because this lubricant can be reused in subsequent forgings or stampings.

Examples are given below for illustrative purposes.

Example 1 EC aluminum scrap containing 2 to 3 copper as impurities was melted into a diameter of 1.32 mr.
7.62 cr diameter with aC0,052 inch) hole
The particles were converted into needle-like particles by separation into a 3-inch rotating cup. rEcJ aluminum refers to aluminum typically used in cables as a current-carrying conductor. The molten metal is at 816°C (1300°F);
The cup was rotated at 1500 r-p, m. The needles were cooled and collected.

The needles had good gloss. Manufactured from tool steel, 4.76 cIn (17/8 inch) xo, 95c
Approximately 1.27c1n (
The needle charge was inserted at a depth of 0.5 inches).

The die was placed in a sealed stainless steel chamber that was evacuated to 711 Dragon Hg (28 inches I(g) and heated to 510°C (950°F). At this temperature the ram was operated to
A pressure of 30,000 psi was applied to the needle for approximately 2 seconds. The die was then removed from the chamber and cracked open to easily remove the compacted molded article having a thickness of approximately 6.35 mm (0.25 inch). The molded article was quickly air cooled at ambient room temperature to a temperature below the recrystallization temperature.

It was found that the needle-like bodies were sufficiently pressed, welded, or held together to form a monolithic molded product having a density approximately equal to the theoretical density of 100 cm. Rockwell hardness values varied from 82 to 85 R/H across different sides of the molded article. The tensile test piece of this molded product was 1538 to 9/crl (
29,875psi) (7) Ultimate tensile strength 1[”13
It had a yield tensile strength of 58 K9/car (19,320 psi). The elongation rate appeared to be about 4.2%. The structure was actually clean, with a precise and smooth exterior surface. When cut in cross section, some elongation of the needles was observed, and a large number of fine crystal grains were observed in each needle. Significant grain growth was observed.

Example 2 Needles produced as described in connection with Example 1 were filled in 89 charges into lubricated tool steel split dies having cavities of the same size. Pressure to 7030 Kq/crii (100,000psi)
Using the same conditions as above but increasing the moldings to 1515 Kg/cr! (
Ultimate tensile strength of 21,555psi) and 13soKy
/crl (19,205 psi) yield tensile strength, 4,
It had an elongation of 4% and a Rockwell hardness of R/H 81-83. Since the molded article was rapidly cooled below the recrystallization temperature after being removed from the die, there was no observable grain growth.

Example 3 Clean aluminum 7075 machined scrap A' was broken and 4.766In (17/8 inch) Xo, 9
A 5 cIn (3/8 inch) die cavity was filled. An 8g charge was heated to 482°C (900'F) K, and the preheated shavings particles were heated to 7030 Kp/ff1 (1
00,000 pst) for less than 5 seconds.

The molded article was extruded and rapidly air cooled to a temperature below its recrystallization. The compacted part was well bonded and had a density of 99.1% of theoretical density and a Rockwell hardness of 94.9. The compact was cleaned with a vibrating cleaner and then ball polished for a mirror finish.

Example 4 250-300 g of needle-like bodies of the type disclosed in Example 1
Charges were placed into a cylindrical die cavity having a diameter of approximately 5.08 cIIL (2 inches) and a length of approximately 5.086 m, (2 inches). The die and particles were heated to 510'C (950
°F) and then the needles were heated to 281.2 Kg/c
It is consolidated into a compacted article having a first predetermined low density, eg, about 85% of the theoretical density, by first compacting at a pressure of ril (4000 ps i ) for about 1 second.

This low-density cylindrical slug is uniform and nearly [1oose J] within the die, and this initially applied pressure primarily collapses the plastic needles while simultaneously causing the needles to collapse within the die. There was a rough movement of the body. During this initial hot compaction, no significant lubricant removal from the die wall was observed and no gelation appeared to occur. This initial hot compacted slag is removed from the die, the die is relubricated, and the low density slag is
3374 Ky/crl (48
,000 psi) for 5 seconds. Then,
The molded article was quickly air cooled below its recrystallization temperature. The final hot pressed molded article was significantly more dense.

Its density increased from the perfect theoretical density of about 85 inches to about 100 inches. Some of the aluminum was forced into the die gap during the second application of pressure.

However, after the second hot compaction operation, gelation of the side die and longitudinal streaks of the slag were not evident. The final molded article was generally uniform in appearance and its Rockwell hardness R/H differed at only two points along its side. Diameter 5.08
σ (2 inches) and length 55-08 (1, (2 inches)
Slag of similar size below at 510°C (950°F)
and 2 s 1.2 Ky/c! ! r4,0OOpsi
) to 85% of the theoretical density. These slags were taken out of the die and heated to 1687 Ky/cril (24,OOOp
By hot pressing again for 5 seconds at a pressure of
A product with full density was obtained. These molded articles were also air cooled below their recrystallization temperature.

In addition to the above-mentioned embodiment, the dimensions are again 47.6 mm (1,
875 inches) x 9.5 (0,375 inches) x 6.
A 0.25 inch long bar was manufactured generally according to the method disclosed in Example 1 and tested to determine the effect of temperature and pressure changes on the formation of hot compression molded articles. Photomicrographs of yet another such example, prepared generally in accordance with Example 1, are shown in FIGS. 11-14.

As explained, temperature is the primary variable, and pressures in excess of those required to compact the molded article to greater than 99% of its theoretical density are relatively unimportant. Generally, the time will not vary significantly beyond 5 seconds, and most molded parts will be kept at a predetermined pressure, such as 15 tsi, 30 tsi, or 5 tsi.
formed in the time necessary to ensure the actual application of 0 tsi. In actual product manufacturing on a commercial scale, the application time only has to be the time to apply pressure to fill all die crevices, solidifying the particles. The particulate material is heated to a higher temperature, e.g. 482°C (90°C).
0″F), for example, 343°C (65°C).
0'F) was found to flow better.

Plastic flow properties occur when the particulate material fills keys, crevices, or narrow cavities and at the same time eliminates voids inside the part, making the part dense and relatively This is important to ensure that it is leak proof. Another consequence of poor plastic flow is the inability to provide a uniform thickness throughout the molded part when hot compressing a flat rectangular bar specimen. 343 these sticks
℃ (650'F), the thickness variation was 0.203 mm as illustrated in the graph shown in Figure 2.
(0,008 inches). By increasing the hot compaction temperature, the plasticity of the heated particles increases, the thickness variation becomes substantial, and the pressure 30 tsi
and decreased to almost zero at 496"C (925°F).

To better understand how temperature and pressure factors affect relative surface finish, the cuboid molded parts described above were tested at 343°C (650°F) and 427°C (800↑).
and 510° C. (950° F.) and at three different pressures: 15 tsi, 30 tsi and 50 tsi.
Manufactured by tsi. Select a completely arbitrary scale from 1 to 10, and
On the other side of this scale, scales below 4 are given to the surface of a smooth, flat, generally solid phase and where the exterior of the particle is very distinct (~. The surface was uneven and not smooth (and flat), indicating that the exterior of the particles was clearly visible. In these poor surface conditions, the particles were loosely intertwined with each other rather than fully intertwined and integrated. Generally, at lower temperatures of 343°C (650″F) and especially at lower pressures, e.g. 15 tsi, surface finish ratings are lower, e.g. 4 and 6; The best result is shown in the graph of Figure 1. Thus, at lower temperatures and pressures, the molded part is somewhat porous and the needles are clearly delineated, and at higher temperatures and pressures. At higher temperatures and pressures above 510°C (950°F) and 30 tsi, the surface finish rating was 8.
~10, the molded product has a sufficiently high density and a porosity of 0.
and the needles were so well integrated that it appeared to be very difficult to discern their contours, especially after cleaning the molded part.

If the pressure used is high enough, e.g.
It is found that even when the temperature varies up to 950'F, it is good, for example 8 or higher. Compression temperature becomes important at lower pressures, eg l 5 tsi. The reason for this is that, as shown in Figure 3, the particles have a surface finish of about 371°C (700°C) to give the desired plastic flow a surface finish of 8 or higher.
(°F). Similarly,
If a compression temperature of 343°C (650″F) is used, good plastic flow is not achieved until a pressure of about 30 tsi is used, as shown in FIG. Sufficient plastic flow to give a good surface finish, i.e. 8 or higher, is between 343°C (650°F) and 51°C.
30tsi and 50t at a temperature of 0°C (950'F')
The best surface finish is obtained at higher pressures of 50
obtained for higher pressures of tsi. in this way,
Higher pressures and temperatures appear to give molded parts with greater plastic flow, denser, and the best surface finish, as shown in Figures 3 and 4.

At the lowest pressures and temperatures shown in Figures 3 and 4, the molded article is porous, the particles are clearly defined and appear to be completely disentangled.

Rockwell hardness will be substantially uniform when the molded article is compressed to substantially sufficient density.

As explained in connection with Figures 5 and 6, a difference of approximately 2 to 4 points for a fully dense hot-pressed molded article is obtained, which is commercially acceptable. . Thus, the graph in Figure 5 shows that the Rockwell hardness, which varies by less than 4, is 15.30 and 50 at 510°C (950"F).
This shows what can be obtained when hot compressed at a pressure of tsi. Similarly, for a molded article hot pressed at 427°C (800°F), the Rockwell hardness is 15.3
<5 for compression pressures of 0 and 50 tsi. On the other hand, if the molded product is, for example, 10 tsj and 343°C (650°C
The hardness of the molded part varies substantially from place to place when it is not completely dense, such as when compressed at ``F), due to the 24 difference between the different Rockwell hardness readings in Figure 5. As shown, however, 50 tsi
At a higher pressure of 343°C (650'F) and a compaction temperature of 343°C (650'F), the molded article is compacted perfectly to give a sufficiently uniform hard product.

It has been found that as the density of the molded article increases, the Rockwell surface hardness of the molded article also increases.As shown in the graph of FIG.
(500°F) to about 510°C (950°F), the density of the product increases and the Rockwell hardness R/H increases from about 75 to 85 R/H.
It increased to H.

The temperature experienced during hot compaction has a significant effect on the tensile strength of the molded article, with higher tensile strengths being obtained for higher temperature hot compaction operations when using a constant pressure. This may be because the product will become denser with higher temperature compaction if a lower, constant compaction pressure, eg 15 tsi, is used. When approximately 100% density is achieved,
As shown in Figure 7 for a compression temperature of 510'C (950°F), a needle hot compression molded article of scrap EC aluminum (containing 2-3% copper as an impurity content) In this case, the molded product weighs 1599 Kg/i (22,70
It had an ultimate tensile strength (UTs) of 0 psi).

These 1599 Kg/J (22,700 psi) UTS die with an elongation of 6.4% and are long enough for an annealing operation to occur. It appeared to have a fully annealed molded microstructure even though it was not held at high temperatures for an extended period of time. The above graph was obtained from data using these EC aluminum molded products.

Tests of molded articles produced by hot compaction of 7075 aluminum shavings particles were similarly carried out at temperatures below the solidus temperature (a
bout the 5 solids temperat
It was shown that increasing tensile strength can be obtained with increasing temperature until ure) J is exceeded. More specifically, the ultimate tensile strength is approximately 399°C (750°F) at 50 tsi.
increases significantly with increasing temperature from 900°F to 482°C. For this alloy, above 482°C (900"F) acid fusion of the particles began, which resulted in a significant decrease in tensile strength as shown in Figure 10.
7075-0 aluminum scrap chips hot pressed for 5 seconds at 2°C (900°F) and 50tsi
It has an ultimate tensile strength of 655.6 KL1/i (52000 psi).

However, these particles were heated to 510°C (950”F)
) and hot compressed at 50 tsi, the ultimate tensile strength is 2460.5 K9/criI (3500
0 psi). This 3655.6 Kg/
The tensile strength of ci (52,000 psi) is 7075
-0 is about 160% larger than that of aluminum rod stock. This 3655.6Ks+/CI? L (52,000p
Looking at the ultimate tensile strength of si) from a different perspective, it is 454℃
(850°F) and solution treatment at 121.1°C (25°C).
approximately 2/3 times that obtained for this alloy after a full T-6 heat treatment consisting of a 25 hour aging at 0°F.

When particles are heated and compressed above about the solidus temperature at which some of the particles melt, the hardness average decreases rapidly and significantly. Thus, 7075 Fulminium shavings range from 482°C (900'F) to 510°C (900'F).
When hot pressed at 50 tsi for 2 seconds at a temperature of 50° F., a decrease in average Rockwell E hardness from 95 to 70 is encountered, as shown in FIG. On the other hand, the average Rockwell hardness ranges from 426°C (800'F) to 482°C (
increases significantly with increasing temperature to 900'F). This is because the molded article becomes denser and harder at higher temperatures up to about the homophase temperature. 482℃ (900℃
A photomicrograph of a molded article made by hot pressing 7075 aluminum shavings that was compressed at 50 tsi for 5 seconds at 50° F. is shown in FIG. The photomicrograph in Figure 13 was made from a longitudinal section etched at 100x magnification. A lamellar structure is visible in FIG. 13, which outlines the swarf with fine isotropic grains within its contour. Unlike the structure disclosed in US Pat. No. 3,076,706, the metal portions do not have any fibrous nature as shown in FIGS. 13 or 14. A cross-sectional view (not shown) shows the absence of specific orientation, highlighting the isotropy found in these molded parts.

The contour of the particles was determined by the method of the present invention at 510°C (9toff
) and 50x micrographs (Figures 11 and 12) of a cross-section taken from an article formed from EC aluminum needle-like particles hot-pressed at 15 tsi for 5 seconds. FIG. 11 is a longitudinal cross-sectional view showing a rigid structure with completely entangled particles without holes, and FIG. 12 is a cross-sectional view of a molded article made from hot-pressed EC aluminum needle-like particles. Figure 14 is a cross-sectional view showing the observable contour as shown in the 200x etched photomicrograph of Figure 14;

It should be noted that in each case of the illustrated micrographs, the structure is actually solid with no holes in it. The matrix looks fine. This is in contrast to powder metallurgy compacts which are porous and usually have some holes visible within them.

Rigid non-porous moldings can be useful in pressurized fluid applications where porous, leaky moldings cannot be used.

For example, dense hot-pressed moldings can be used in hydraulic or pneumatic lines that must be relatively leak-tight to the pressurized liquid conveyed therein. Generally, molded articles made from aluminum by sintered powder metallurgy or die casting have leakage and have not been used for such purposes. For example, wa ga 3.18
A hot-pressed aluminum specimen with a wall thickness of only mm ('/B inch) was tested and 175.8 K9/d
For hydraulic oil pressurized at t (2500 psi),
and 28.1Kg/crl (400pai) K
It was found to be leak-proof against pressurized retahelium scum. This leak resistance along with improved strength properties makes these hot-pressed moldings (with or without subsequent formation by forging) superior to conventional aluminum die-cast or powder metallurgy moldings. This allows it to be used in applications that were previously impossible.

Although most of the experiments in this example have been conducted with aluminum or aluminum alloy particles, these tests were conducted to demonstrate that other metals can also be hot compacted according to the method of the present invention; Examples include, but are not limited to, magnesium, copper, and iron. Further examples are presented for illustrative purposes.

Example 5 Substantially pure magnesium was deposited in a length of 1.59 mtn (
(16 inch) to 318 dragon (1/8 inch) approximately 36
Cut into small pieces with a surface area to volume ratio of 0.

The split die described and used above was used with a magnesium charge of about 3.1059. The particles are heated to approximately 482°C (900°F)
) and compressed between the upper and lower rings, but during that time 71
It was placed in a stainless steel sealed chamber evacuated to 1.2 mrxH'i (28 inches Hg). The bar was compressed for 2 seconds at 24 tsi in a preheated die at approximately 482°C (90°T). The die was then removed from the chamber, split open, and the compressed molded article was removed and air cooled to an ambient room temperature below the recrystallization temperature. The surface finish was good. 6.
An elongation of 5.2% was obtained at 35 tnm ('/4 inch). The compressed density was approximately 97.6 and the Rockwell hardness on the H scale was 28. Dimensions are approximately 4. ．．
57cIrL (1,S inch), width approx. 9.4mm (0,
3 inches) and thickness 3.81 mm (0.15 inches)
When the test rod was pulled, it was approximately 1912Kp/cnIr2
It gave an ultimate tensile strength of 7.200 psi). The structure looked clean and in fact I couldn't see any holes in it.

When we used the same magnesium material and changed only the pressure to 12 tsi, we found that the ultimate tensile strength was considerably lower, i.e., 629.9 Ky/d (8,960 psi).Also, the hardness was 65, and the density for the hot pressed magnesium molded article was 98.996. Figure 15 is a photomicrograph of a 100x etched cross section of the magnesium molded article compressed at 12 tsi.

Example 6 Magnesium wire, which appears to be a two-layer alloy consisting primarily of magnesium, is similarly hot pressed to a length of approximately 4.57 cm (1.8 inches) and a width of 9.4 mm (o.
Test bars were molded with a width of 0.3 inches (3 inches) and a width of 4.06 inches (0.16 inches). These rods are also the same (,482℃ (90
0°F) for 2 seconds under a pressure of 24 tsi. The linear particles had a surface area to volume ratio of approximately 50. The particles were preheated to approximately 482°C (900°F) and the splitting die was also preheated. The resulting test bar weighed approximately 3.1 g and 1.8
It had a volume of cr. The bar had a smooth exterior surface. An elongation of 32 inches was obtained at 6.35 m1+ (1/4 inch). The bar had a density of about 102.1% and a Rockwell B hardness of about 34. This density value in excess of 100 inches was caused by the inclusion of oxides in the molded article being weighed. The tensile test piece from this molded product was approximately 8
50.6 K9/Cl71! (12,100psi
) had an ultimate bow tensile strength of

Using the same magnesium wire, 482°C (900°F)
When hot-pressed for 2 seconds, but at a lower pressure of 12 tsf, the magnesium hot-pressed product was 98.2 tsf.
% density, 41 hardness and 239Kg cleaning (3400p
It had an ultimate tensile strength of si).

This is a microscopic photograph of this magnesium hot compression molded product.
As seen in Figure 16, the structure was generally clean with no holes observed.

Magnesium particles having an SA/V ratio of about 180 were similarly hot pressed as described above in connection with Examples 5 and 6, and the molded articles had a good surface finish of 8 and about 6
It had a Rockwell hardness of 7. The ultimate tensile strength was approximately 911.8 Kg/cn (12,970 psi). The molded article was 6.35 mm (1/4 inch) and had an elongation of 2.8%.

The same magnesium particles with an SA/V relationship of about 180 were heated at 482°C (900°F) for 2 seconds but at 12 tsi
The ultimate tensile strength of the molded article compressed at 24 tsi is 911. , 8 Kg/c++! (12,97
0psi) only about 90. OKp/CI? L
(1,280 psi). This was apparently due to more incomplete welding of the particles when hot compacted at this pressure.

In another example, magnesium powder having an SA/V ratio of about 3500 is heated at 482°C (900°F) and 12 ts
It was hot-pressed at l. These latter molded articles made from magnesium powder had a Rockwell hardness rating of -3 on the H scale and were too soft. U, T
, S, 90.0 K9/cIL (1,280 ps
i) to 693 K9/cd (9860 psi), and it appears that the presence of large amounts of surface oxides and other impurities caused this problem.

24 tsi (・, molded products manufactured from powder are 9
Hardness of 5, density of 105.2, 1310 Ky/1 (1
Ultimate tensile strength of 8,630 psi) and 635 psi
4 inches) and had an elongation rate of 2.0%.

In general, better results appear to be obtained by hot compacting the powder at higher pressures, such as 24 tsi, and using powders with fewer oxides than the powders used and described above. When the pressure is increased from 12 tsi to 24 tst, the ultimate tensile strength generally increases from 90 to 900
The hardness and density values did not change appreciably.

A further example according to the invention is shown below, instead of hot pressing of copper.

Example 7 A generally spherical body of copper shot consisting of substantially pure copper metal having an SA/V ratio of about 100 was heated to about 510°C (95°C).
Preheat the molding die to 510°C (9°F).
50'F). A charge of 24.039 particles is inserted into the die and heated at approximately 510° for approximately 50 tsi for approximately 1 second.
Compressed at 950°F. The molded articles had a surface finish rating of about 7, and these molded articles had a density of about 962. Rockwell B scale hardness is 23
Met. It has dimensions of length 47.32 mm (1,863 inches), width 9.68 mm (0.381 inches) and width 6.1 mm (0°240 inches), and measures approximately 2.792 CC (7 mm).
) A test bar with a volume was pulled. It appears that the copper shot particles contained too many oxides, and better results would have been obtained using cleaner copper particles.Oxides appear to make the moldings more brittle. be.

Similarly, copper particles were used here at 510""C (950°
F) Hot pressing at a higher temperature appears to be desirable. Furthermore, by compacting the copper powder it was found to have a good clean-looking structure as well as a density in the range of about 95.7-98.7% and a Rockwell B hardness of 12-51. No tensile strength test data were obtained for hot-pressed copper moldings. A cross-sectional view is shown in FIG.

It has been found that iron powder can also be hot compacted according to the method of the invention. More specifically, a preheated carbonyl powder having an SA/V ratio of 50,800 was heated to 510°C (950°F).
), then 510°C for about 1 second at 50 tsi.
(950°F) in a preheated die. The resulting density was approximately 95.5% of the theoretical perfect M degree, and the molded article had a Rockwell hardness (Rc scale) of approximately 480). It weighs about 24.483g and weighs 47.4 meters (1
, 86 inches) length, 9.65 mm (0,380
Tensile strength specimens having a width of 0.280 inches and a thickness of 7.11 mm (0.280 inches) were pulled. It appears that some excess carbon was absorbed during processing, making this specimen significantly brittle. This molded article broke many times in the test grip of a tensile strength tester. Gauge length area durable tensile load is 2509/(-1d (35,690psi)
Met.

15. A coarser powder of carbonyl having an SA/V ratio of 200 was also preheated to 510°C (950”F) and
50 tst in a die preheated to 10°C (950°F)
It was hot compressed for 1 second. The formed article has a density of approximately 98.6% of the theoretical density and approximately 1 on the Rockwell C scale.
It had a hardness of 3. A tensile test bar of approximately the same size as the one described above was pulled to 6765.7 to 9/ctl (96
, 240psi) U, T, S.

obtained, which is virtually as high as pure iron moldings.

These results range from approximately 982'C (1800°F) to 10
It appears that particles of iron other than carbonyl iron at higher temperatures of 93°C (2000°F) will give satisfactory results.

From the experiments conducted, 982°C (1800°F) ~ 109
It appears that other metal particles, such as nickel at 3°C (2000°F), can be hot compacted to form deformed nickel parts by isothermal heating of the particles and die. Similarly, molybdenum and tungsten particles preheated to about 1649°C (3000”F)
It must be capable of being hot compressed in a die heated to 3000°F. The pressure used was 12,000
tsi has to be raised, better result is about s
o, oo.

tsi should be obtained at higher temperatures. In order to withstand such temperatures and pressures, the die material may need to be made of a refractory material. The duration of high pressure application must be less than a few seconds, in contrast to prior art long-duration sintering methods where pressure is applied for less than a few minutes or even half an hour. (hot pressing
) The term J refers to the simultaneous application of heat and pressure for short periods of time, which is distinct from long-duration sintering methods. Similarly, hot compaction is distinctly different from methods of rolling particles, such as those described in the above-mentioned patents, in which the particles are extruded or drawn to form a fibrous structure while entering and passing through a roller nip. must be maintained.

The hot compaction method described above may be further supplemented by adding other materials to the particles themselves or to the die cavity. For example, the cost of the metal can be lowered by adding less expensive filler materials before producing the gold PA particles. Preferably such fillers (σ) have a density close to that of the molten metal to which they are added in order to give more homogeneous properties to the filled metal particles to be subsequently hot compacted. Additional strength can be obtained by adding reinforcing materials to the die for incorporation into the molded article.

For example, carbon fibers can be added to the mold in layers or groups to intertwine into metallic moldings, thus providing additional strength to the molding. In this, the carbon fibers remain elongated and provide their maximum strength to the molded part. It is believed that carbon fibers having a volume of about 10 to 40 inches can be placed in a mold and suitably hot compressed.

Preferred larger particles reduce the aluminum particle size to SA/V
When increasing from 1500 to about 3, it appears that the obtained hardness usually gives better light rice than smaller particles as evidenced by higher tensile strength. All SA/V ratios disclosed herein are obtained by measuring the nominal diameter in inches and then calculating the surface area and volume for typically spherical particles. S.A.
/V ratio numbers have units of 10-1 inches not included here. Of course, if measurements were taken in the metric system, the number defining the particle size would also change, with units of 1O
-1 crrL. In general, strength, hardness, and/or other properties may be lower (lower strength, hardness, and/or Powders can be used in this method only if they are not available.

Powders can also be used in the method of the invention, since in some cases moldings of lower strength or hardness are sufficient.
It falls within some areas of the scope of the claims of the invention.

[Industrial applicability]

It will be seen from the above description that a new method has been found for producing plastically worked metal moldings with good strength, narrow dimensional tolerances and good surface properties. This process is economically attractive in that scrap metal can be used and that alloyed metals, such as aluminum alloys, can be used as particles as well as pure metals. Furthermore, additives such as carbon fiber additives can be added to the metal particles to improve the strength of the molded article or, in the case of fillers, to reduce the cost of metal in the molded article. This method lends itself to a high production output from the press, and the molded parts, e.g. preforms, are immediately transferred from this hot press while still hot for further processing, e.g. heat treatment in a press or forging. be done. On the other hand, hot molded articles can be air cooled or quenched to quickly return below their recrystallization temperature to prevent substantial grain growth that would reduce their hardness and tensile strength.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus for carrying out the method of hot compaction of metal or metallic particles according to the present invention. FIG. 2 is a graph showing the effect of temperature change on the difference in thickness of molded articles manufactured according to the present invention. FIG. 3 is a graph showing the effect of temperature changes on the surface finish of hot-pressed molded articles made in accordance with the present invention. FIG. 4 is a graph showing the effect of pressure on the surface finish of molded articles made in accordance with the present invention. FIG. 5 is a graph showing the effect of pressure on the difference in Rockwell 1 hardness between different locations in a molded article made in accordance with the present invention. FIG. 6 is a graph showing the effect of temperature change on the Rockwell hardness of molded articles manufactured according to the present invention. FIG. 7 is a graph showing the effect of temperature change on the ultimate tensile strength of molded articles made according to the present invention. FIG. 8 is a graph showing the effect of pressure changes on the flash thickness of molded articles manufactured according to the present invention. FIG. 9 is a graph showing the effect on Rockwell hardness of molded articles hot compacted at temperatures below and substantially above the solidus temperature. FIG. 10 is a graph showing the influence of hot compression on &i limit tensile strength at temperatures below and above the in-phase temperature. Fig. 5 Fig. 6 Fig. 3 Chili 0Cho upper 1A 4↑ Baijia Benli 7 Fig. 9 Procedural amendment 1゜Representation of the matter 1999 Patent Application No. 177841 2, Title of the invention Hot compression method for powder and granules 3, relationship with the case of the person making the amendment Patent applicant address name Title: IIT Research Institute, Shin-Otemachi Building, Ward 206, type-printed specification

Claims (1)

[Claims] 1. (a) Lubricating the wall surface of the die cavity; (b) heating the metal powder or metal alloy powder to a temperature ranging from approximately the recrystallization temperature to the solidus temperature of the metal or alloy; (c) hot-compacting the heated granules at a first pressure in a first heated and lubricated portion of the die cavity to substantially transform the granules into a molded article; (d) compressing the molded article at a second pressure higher than the first pressure in the other portion of the die cavity; A method for manufacturing a molded article with high dimensional accuracy of the powder or granular material, comprising the steps of: 2. The granular material is aluminum or aluminum alloy particles having a minimum dimension of at least 1000 microns in one direction, and the molded article is heated to the recrystallization temperature after the compression process and before recrystallization and grain growth occur. 2. The method of claim 1, further comprising the step of cooling. 3. The method according to claim 2, wherein the particles and the die are each preheated to 400°C to 600°C.